First Identification and Chemical Modeling of New Thiol ($-$SH) Bearing Molecule in the Interstellar Medium: Dithioformic Acid

Abstract

The study of complex organic molecules containing thiol ($-$SH) groups is essential in interstellar media because $-$SH plays an important role in the polymerization of amino acids (R-CH(NH${}_2$)-COOH). Some quantum chemical studies have shown that there is a high chance of detecting the emission lines of dithioformic acid (HC(S)SH) in the highly dense and warm-inner regions of hot molecular cores and hot corinos. Therefore, we attempted to search for the emission lines of HC(S)SH toward the highly dense hot corino object NGC 1333 IRAS 4A using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 7. We present the first detection of the rotational emission lines of the trans-conformer of dithioformic acid (t-HC(S)SH) toward the NGC 1333 IRAS 4A2. The column density and excitation temperature of the t-HC(S)SH toward NGC 1333 IRAS 4A2 are (2.63$\pm$0.32)$\times$10${}^{15}$ cm${}^{-2}$ and 255$\pm$32 K, respectively. The fractional abundance of t-HC(S)SH with respect to H${}_2$ is (2.53$\pm$0.68)$\times$10${}^{-9}$. The column density ratio of t-HC(S)SH and t-HCOOH toward NGC 1333 IRAS 4A2 is 0.36$\pm$0.02. To understand the possible formation pathways of HC(S)SH, we computed a two-phase warm-up chemical model abundance of HC(S)SH using the gas-grain chemical code UCLCHEM. After chemical modeling, we claim that HC(S)SH is formed in NGC 1333 IRAS 4A2 via barrierless radical--radical reactions between CSSH and H on the grain surfaces.

arXiv commentPublished in ACS Earth and Space Chemistry

References in corpus (28)

• The chemical composition of the Sun
• A three-phase chemical model of hot cores: the formation of glycine
• An Accurate Flux Density Scale from 50 MHz to 50 GHz
• Evaporation of ices near massive stars: models based on laboratory TPD data
• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• Complex molecules in the hot core of the low mass protostar NGC1333-IRAS4A
• On the reservoir of sulphur in dark clouds : chemistry and elemental abundance reconciled
• Constraining the abundances of complex organics in the inner regions of solar-type protostars
• Modeling Sulfur Depletion in Interstellar Clouds
• UCLCHEM: A Gas-Grain Chemical Code
• Spectroscopic characterization and detection of Ethyl Mercaptan in Orion
• Thiols in the ISM: first detection of HC(O)SH and confirmation of C${}_2$H${}_5$SH
• A new study of an old sink of sulfur in hot molecular cores: the sulfur residue
• A line confusion-limited millimeter survey of Orion KL. III. Sulfur oxide species
• Polysulfanes on interstellar grains as a possible reservoir of interstellar sulphur
• Implications of a hot atmosphere/corino from ALMA observations towards NGC1333 IRAS 4A1
• Seeds of Life in Space (SOLIS). VI. Chemical evolution of sulfuretted species along the outflows driven by the low-mass protostellar binary NGC1333-IRAS4A
• The trans/cis ratio of formic, HCOOH, and thioformic, HC(O)SH, acids in the Interstellar Medium
• The first bird's-eye view of a gravitationally unstable accretion disk in high-mass star formation
• Chemical modelling of glycolaldehyde and ethylene glycol in star-forming regions
• The Infall Motion in the Low-Mass Protostellar Binary NGC 1333 IRAS 4A1/4A2
• Identification of the simplest sugar-like molecule glycolaldehyde towards the hot molecular core G358.93-0.03 MM1
• The chemical structure of the Class 0 protostellar envelope NGC 1333 IRAS 4A
• Accurate millimetre and submillimetre rest frequencies for $cis$- and $trans$-dithioformic acid, HCSSH
• Constraints of the formation and abundances of methyl carbamate, a glycine isomer, in hot corinos
• Detection of antifreeze molecule ethylene glycol in the hot molecular core G358.93$-$0.03 MM1
• Detection of monothioformic acid towards the solar-type protostar IRAS 16293-2422
• ACA observation and chemical modelling of phosphorus nitride (PN) towards the hot molecular cores G10.47+0.03 and G31.41+0.31

Cited by in corpus (2)

• First detection of ethylene oxide and acetaldehyde in hot core G358.93$-$0.03 MM1: Tracing prebiotic oxygen chemistry
• Organic Acid Chemistry in ISM: Detection of Formic Acid and its Prebiotic Chemistry in Hot Core G358.93$-$0.03 MM1